Could fluoride in drinking water really affect IQ? A massive new study says no

Fluoride has been a hot topic lately, with Secretary of Health and Human Services Robert F. Kennedy Jr. making it clear that he is not in favor of the longstanding public health recommendation of adding the mineral to drinking water. Some states, like Utah and Florida, have moved to restrict or reconsider fluoride in drinking water, citing concerns that fluoride would impact the IQ of children, among other fears.

That concern stems from a widely debated scientific paper published in 2025 that linked high levels of fluoride in water to lower IQs in children—but at levels that far exceeded what appears in American drinking water. (More on that in a moment.)

Just a refresher: Fluoride is a naturally occurring mineral that’s present in rivers, lakes, and oceans, as well as in some foods and drinks, per the American Dental Association (ADA). It is referred to as “nature’s cavity fighter” because it helps to protect against tooth decay. Fluoride is in many dental products, including toothpaste and mouthwash. Most communities in America have added small amounts of fluoride to their water systems in a practice known as “fluoridation” for those dental health benefits, and data has shown that this reduces cavities.

But now, new research published in Proceedings of the National Academy of Sciences finds no evidence that low levels of fluoride added to community drinking water affect children’s IQ or brain function later in life. Here’s what experts want you to know.

Meet the experts: Gina Rumore, PhD, study co-author and a researcher at the University of Minnesota; Julie Meyerson, DMD, a dentist in New York City; Kelly Johnson-Arbor, MD, a toxicologist at MedStar Health; and Jamie Alan, PhD, associate professor of pharmacology and toxicology at Michigan State University.

What did the study find?

For the study, researchers analyzed data from 10,317 Wisconsin high school seniors from 1957 to 2021 (up until the oldest participants were 80 years old). The team estimated when participants were first exposed to fluoride in their water (if at all), and tracked their IQ scores or other cognitive function measures over time.

After analyzing the data, researchers found there was no evidence of an association between exposure to fluoride at any point and differences in IQ or cognitive function over time.

The analysis was inspired by the controversial 2025 study, explains Gina Rumore, PhD, study co-author and researcher at the University of Minnesota. “We had some data that we could look at early life exposure and later life outcomes,” she says. “What we found was…nothing.”

Why has fluoride been so misunderstood?

While some of the recent concerns around fluoride have been linked to the MAHA movement, Rumore says there have actually been fears surrounding fluoride in drinking water going back decades, as far as the 1950s, when people linked fluoride to communism.

But scientific data can also just be misinterpreted, says Jamie Alan, PhD, an associate professor of pharmacology and toxicology at Michigan State University. “Sometimes it is hard to interpret scientific data if you don’t see the whole picture,” she says. “It is important to consider all the variables that are measured in any study.”

That widely cited (and misinterpreted) 2025 study was based on a review of studies that were conducted outside the U.S., where fluoride concentrations in drinking water are “significantly higher,” says Kelly Johnson-Arbor, MD, a toxicologist at MedStar Health. “This may have resulted in confusion, misinterpretation, and misinformation related to the article’s conclusions,” she says.

Why fluoride is important

Fluoride is “essential” for dental health, according to Julie Meyerson, DMD, a dentist in New York City. “It strengthens enamel at a microscopic level and helps prevent cavities,” she says. During the day, acids produced by oral bacteria and sugars cause demineralization, a process where important minerals like calcium and phosphate are stripped from your tooth’s surface, she explains.

“Fluoride promotes remineralization by helping redeposit these minerals back into the enamel in a more acid-resistant form known as fluorapatite, making teeth harder and less susceptible to future acid attacks,” Meyerson says.

Fluoride also has an antimicrobial effect on teeth to limit the ability of cavity-causing bacteria to break down sugars and produce acids, Meyerson says. “This dual action of rebuilding enamel and limiting bacterial activity makes fluoride one of the most effective and well-researched tools available for preventing tooth decay,” she adds.

Rumore says that the evidence is “pretty clear” that fluoride in drinking water does not negatively impact IQ. “It’s really important to have research on this,” she says.